OnabotulinumtoxinA alone provides relief from chronic migraine, and addition of anti-calcitonin gene-related peptide (CGRP) antibodies may boost the benefit, according to a large retrospective analysis. The results lend hope that the combination may be synergistic, according to Andrew Blumenfeld, MD, director of the Headache Center of Southern California in Carlsbad. Blumenfeld presented at the American Headache Society’s 2021 annual meeting. The study was published online April 21 in Pain Therapy.
The retrospective analysis showed a 4-day reduction in headache days per month. In contrast, in the pivotal study for erenumab, the most commonly used anti-CGRP antibody among subjects in the study, showed a 2-day benefit in a subanalysis of patients who had failed at least two oral preventives.
There is mechanistic evidence to suggest the two therapies could be synergistic. OnabotulinumtoxinA is believed to inhibit the release of CGRP, and antibodies reduce CGRP levels. OnabotulinumtoxinA prevents activation of C-fibers in the trigeminal sensory afferents, but does not affect A-delta fibers.
On the other hand, most data indicate that the anti-CGRP antibody fremanezumab prevents activation of A-delta but not C-fibers, and a recent review argues that CGRP antibody nonresponders may have migraines driven by C-fibers or other pathways. “Thus, concomitant use of medications blocking the activation of meningeal C-fibers may provide a synergistic effect on the trigeminal nociceptive pathway,” the authors wrote.
Study Finding Match Clinical Practice
The results of the new study strengthen the case that the combination is effective, though proof would require prospective, randomized trials. “I think that it really gives credibility to what we are seeing in practice, which is that combined therapy often is much better than therapy with onabotulinumtoxinA alone, said Deborah Friedman, MD, MPH, who was asked to comment on the findings. Friedman is professor of neurology and ophthalmology at the University of Texas, Dallas.
The extra 4 migraine-free days per month is a significant benefit, said Stewart Tepper, MD, professor of neurology at the Geisel School of Medicine at Dartmouth, Hanover, N.H. “It’s an extra month and a half of no disability per year, and that’s on top of what onabotulinumtoxinA does. So it’s really a very important clinical finding,” Tepper said in an interview.
Many insurance companies refuse to pay for the combination therapy, despite the fact that relatively few migraine patients would likely seek it out, according to Friedman. “It’s just kind of a shame,” she said.
Insurance companies often object that the combination therapy is experimental, despite the widespread use of combination therapies in migraine. “It’s no more experimental in my opinion than any other combination of medications that we use. For people that have severe migraine, we use combination therapy all the time,” said Friedman.
Improvements With Combination Therapy
The study was a chart review of 257 patients who started on onabotulinumtoxinA and later initiated anti-CGRP antibody therapy. A total of 104 completed four visits after initiation of anti-CGRP antibody therapy (completers). Before starting any therapy, patients reported an average of 21 headache days per month in the overall group, and 22 among completers. That frequency dropped to 12 in both groups after onabotulinumtoxinA therapy (overall group difference, –9 days; 95% confidence interval, –8 to –11 days; completers group difference, –10; 95% CI, –7 to –12 days).
A total of 77.8% of subjects in the overall cohort took erenumab, 16.3% took galcanezumab, and 5.8% took fremanezumab. In the completers cohort, the percentages were 84.5%, 10.7%, and 4.9%, respectively.
Compared with baseline, both completers and noncompleters had clinically significant improvements in disability, as measured by at least a 5-point improvement in Migraine Disability Assessment (MIDAS) score at the 3-month visit (–5.8 for completers and –6.3 for the overall cohort group), the 6-month visit (–6.6 and –11.1), the 9-month visit (–8.3 and –6.1), and 1 year (–12.7 and –8.4).
At the first visit, 33.0% of completers had at least a 5-point reduction in MIDAS, as did 36.0% of the overall cohort group, and the trend continued at 6 months (39.8% and 45.1%), 9 months (43.7% and 43.7%), and at 1 year (45.3% and 44.8%).
The study was funded by Allergan. Blumenfeld has served on advisory boards for Aeon, AbbVie, Amgen, Alder, Biohaven, Teva, Supernus, Promius, Eaglet, and Lilly, and has received funding for speaking from AbbVie, Amgen, Pernix, Supernus, Depomed, Avanir, Promius, Teva, Eli Lilly, Lundbeck, Novartis, and Theranica. Tepper has consulted for Teva. Friedman has been on the advisory board for Allergan, Amgen, Lundbeck, Eli Lilly, and Teva Pharmaceuticals, and has received grant support from Allergan and Eli Lilly.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
Medscape Medical News © 2021 WebMD, LLC
Cite this: Botox, CGRP a Dynamic Duo for Migraine? - Medscape - Jun 09, 2021.